Influence of Depth and Site-specific Ecological Factor on Shell Morphometrics and Coloration in Green Mussels (Perna viridis)

Abstract

The green mussel (Perna viridis) is a commercially valuable bivalve with strong aquaculture potential in Bangladesh. This study examined how water depth and site-specific ecological factors influence shell morphometrics and coloration in P. viridis. A total of 450 mussels were cultured at three depths (0.5 m, 1.0 m, and 1.5 m) across three coastal sites Khurushkul, Moheshkhali, and Chowfaldandi. Monthly monitoring of water quality was conducted throughout the study from October 2024 to March 2025. Shell shape and size variations were assessed using geometric morphometric techniques, while shell coloration was analyzed through RGB, HSV, and CIELAB color models. The results revealed significant differences in shell morphology and pigmentation across both site and depth. Mussels from Chowfaldandi displayed broader shells, while those from Khurushkul had a more streamlined form, reflecting local water dynamics. Deeper-dwelling mussels tended to develop rounder, more inflated shells, possibly as an adaptation to calmer, low-light environments. Coloration also varied notably: darker green pigmentation was observed in mussels from shallow depths and from Moheshkhali, likely associated with higher chlorophyll a concentrations and clearer water. In contrast, mussels from Chowfaldandi showed paler shells, potentially due to reduced light penetration and limited food supply. These findings demonstrate how environmental conditions shape key shell traits in P. viridis, offering insights for site and depth selection to enhance growth and shell quality in aquaculture. Shell morphology and pigmentation serve as valuable indicators for assessing habitat suitability and environmental quality.